1. Field of the Invention
The present invention relates to a filter and an ink-jet recording apparatus having the same.
2. Background Art
In ink-jet recording apparatuses, ink stored in an ink container of the main body is pumped into a nozzle of an ink discharge head by a feed pump. During operation, ink is continuously discharged from a discharge orifice of the nozzle and broken into particles. Among ink particles discharged from the nozzle, those used for printing are electrostatically charged and deflected, and then land on a print medium to form text thereon. Meanwhile, ink particles not used for printing are not electrostatically charged or deflected, but travel into an opening of a gutter that is located along the direction straight ahead of the discharge orifice of the nozzle, and are collected into the ink container by a recovery pump for re-use purposes.
There are cases in which foreign substances adhere to the inner side of the discharge orifice of the nozzle or to the circumference thereof during operation, whereby the direction of ink discharged from the discharge orifice could change. In such cases, ink particles not used for printing could deviate from the opening of the gutter, thereby contaminating the inner side of the ink discharge head, production facilities, products, and the like, or the discharge orifice could become clogged, thereby preventing ink from being discharged or printed. Examples of foreign substances include dust in air that is sucked into the gutter during operation and dust in air that enters an ink supply unit while ink is being supplied. Such dust will reach the nozzle through the channel of the ink. In order to remove such foreign substances, the ink-jet recording apparatus has a filter provided in the channel upstream of the nozzle.
FIG. 1 illustrates an exemplary structure of a conventional filter. As illustrated in FIG. 1, a conventional filter 700 includes a capsule member 701 with a connecting port 711 and a capsule member 702 with a connecting port 712 that are joined together in the form of a single capsule. Within the capsule is provided a cylindrical filter medium 703. One end face of the filter medium 703 is joined to the capsule member 701 and the other end face thereof is joined to a cap member 704. The two connecting ports communicate with each other through the filter medium 703. The two connecting ports of the filter 700 face opposite directions. Thus, there is a possibility that when the old filter is removed for the purpose of being replaced with a new one in filter exchange operation, drops of ink remaining in the old filter could contaminate the surrounding area.
As a filter that solves the aforementioned problem, a filer having two connecting ports that face the same direction has been considered. FIG. 2 illustrates an exemplary structure of such a conventional filter. As illustrated in FIG. 2, a filter 500 has a top capsule member 501 with two connecting ports (i.e., a central connecting port 511 and a peripheral connecting port 512) and a bottom capsule member 502 that are joined together in the form of a single filter capsule. One end face of a cylindrical filter medium 503 provided in such a filter capsule is joined to the capsule member 501 and the other end face thereof is joined to a cap member 504. Since the two connecting ports of the filter 500 face the same direction, there is an advantage in that it is possible to reduce the possibility of contaminating the surrounding area with ink drops by adjusting the orientations of the two connecting ports such that they face upwards in removing the old filter in filter exchange operation.
FIG. 3 is a systematic diagram of an ink circulation system that uses the filter 500. The filter 500 is disposed in a channel 680 between an ink container 601 and a nozzle 651 with a feed pump 611 interposed between the filter 500 and the ink container 601. In addition, a branch 641 leading to a channel 682 that communicates with a suction port of a recovery pump 613 is disposed in a channel 681 between the filter 500 and the nozzle 651.
In removing the old filter in filter exchange operation, it is necessary to remove the ink remaining in the filter in order to reduce the possibility of contaminating the surrounding area with the ink. FIG. 4 illustrates the flow of ink in removal of the ink. In FIG. 4, the ink container is exposed to air. With such a flow, ink in the ink container or ink channel is displaced by air so that the ink is discarded to the outside of the apparatus. FIG. 5 illustrates the orientation of the filter in removal of the ink. As illustrated in FIG. 5, the orientation of the filter 500 is set so that the two connecting ports thereof (i.e., the central connecting port 511 and the peripheral connecting port 512) face the horizontal direction with the peripheral connecting port 512 located on the lower side of the central connecting port 511. Ink flows in the direction from the central connecting port to the peripheral connecting port 512. Since the ink located above the peripheral connecting port 512 of the filter during removal of the ink is displaced by air, almost all the ink can be discharged.
Meanwhile, after the ink is removed and the filter is replaced with a new one, it is necessary to remove air from the new filter. Removal of air is necessary in order to prevent the residual air from flowing out of the filter and thereby reaching the nozzle during operation, which could otherwise cause ink splattering when it is discharged from the discharge orifice, and thus could contaminate the inner side of the ink discharge head, production facilities, products, and the like, or ink particles may not be deposited onto a desired place, resulting in abnormal printing. FIG. 6 illustrates the flow of ink in removal of air. With such a flow, an ink channel is filled with ink of an ink supply reservoir. FIG. 7 illustrates the orientation of the filter in removal of air. As illustrated in FIG. 7, the orientation of the filter 500 is set so that the two connection ports thereof face the horizontal direction with the peripheral connecting port 512 located on the upper side of the central connecting port 511. Upon entry of ink into the central connecting port 511, air is discharged from the upper peripheral connecting port 512. Thus, almost all the air in the filter can be displaced by the ink.    [Reference 1] JP Patent Publication (Kokai) No. 2004-230321 A